<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
 <head>
  <meta http-equiv="content-type" content="text/html; charset=UTF-8">
  <title>Execute an external program and display the output</title>

 </head>
 <body><div class="manualnavbar" style="text-align: center;">
 <div class="prev" style="text-align: left; float: left;"><a href="function.shell-exec.html">shell_exec</a></div>
 <div class="next" style="text-align: right; float: right;"><a href="book.pthreads.html">pthreads</a></div>
 <div class="up"><a href="ref.exec.html">Program execution 函数</a></div>
 <div class="home"><a href="index.html">PHP Manual</a></div>
</div><hr /><div id="function.system" class="refentry">
 <div class="refnamediv">
  <h1 class="refname">system</h1>
  <p class="verinfo">(PHP 4, PHP 5)</p><p class="refpurpose"><span class="refname">system</span> &mdash; <span class="dc-title">Execute an external program and display the output</span></p>

 </div>

 <div class="refsect1 description" id="refsect1-function.system-description">
  <h3 class="title">说明</h3>
  <div class="methodsynopsis dc-description">
   <span class="type">string</span> <span class="methodname"><strong>system</strong></span>
    ( <span class="methodparam"><span class="type">string</span> <code class="parameter">$command</code></span>
   [, <span class="methodparam"><span class="type">int</span> <code class="parameter reference">&$return_var</code></span>
  ] )</div>

  <p class="para rdfs-comment">
   <span class="function"><strong>system()</strong></span> is just like the C version of the
   function in that it executes the given
   <em><code class="parameter">command</code></em> and outputs the result.
  </p>
  <p class="para">
   The <span class="function"><strong>system()</strong></span> call also tries to automatically
   flush the web server&#039;s output buffer after each line of output if
   PHP is running as a server module.
  </p>
  <p class="para">
   If you need to execute a command and have all the data from the
   command passed directly back without any interference, use the
   <span class="function"><a href="function.passthru.html" class="function">passthru()</a></span> function.
  </p>
 </div>


 <div class="refsect1 parameters" id="refsect1-function.system-parameters">
  <h3 class="title">参数</h3>
  <p class="para">
   <dl>

    
     <dt>
<em><code class="parameter">command</code></em></dt>

     <dd>

      <p class="para">
       The command that will be executed.
      </p>
     </dd>

    
    
     <dt>
<em><code class="parameter">return_var</code></em></dt>

     <dd>

      <p class="para">
       If the <em><code class="parameter">return_var</code></em> argument is present, then the
       return status of the executed command will be written to this
       variable.
      </p>
     </dd>

    
   </dl>

  </p>
 </div>


 <div class="refsect1 returnvalues" id="refsect1-function.system-returnvalues">
  <h3 class="title">返回值</h3>
  <p class="para">
   Returns the last line of the command output on success, and <strong><code>FALSE</code></strong>
   on failure.
  </p>
 </div>


 <div class="refsect1 examples" id="refsect1-function.system-examples">
  <h3 class="title">范例</h3>
  <p class="para">
   <div class="example" id="example-3586">
    <p><strong>Example #1 <span class="function"><strong>system()</strong></span> example</strong></p>
    <div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #007700">echo&nbsp;</span><span style="color: #DD0000">'&lt;pre&gt;'</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">//&nbsp;Outputs&nbsp;all&nbsp;the&nbsp;result&nbsp;of&nbsp;shellcommand&nbsp;"ls",&nbsp;and&nbsp;returns<br />//&nbsp;the&nbsp;last&nbsp;output&nbsp;line&nbsp;into&nbsp;$last_line.&nbsp;Stores&nbsp;the&nbsp;return&nbsp;value<br />//&nbsp;of&nbsp;the&nbsp;shell&nbsp;command&nbsp;in&nbsp;$retval.<br /></span><span style="color: #0000BB">$last_line&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">system</span><span style="color: #007700">(</span><span style="color: #DD0000">'ls'</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$retval</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">//&nbsp;Printing&nbsp;additional&nbsp;info<br /></span><span style="color: #007700">echo&nbsp;</span><span style="color: #DD0000">'<br />&lt;/pre&gt;<br />&lt;hr&nbsp;/&gt;Last&nbsp;line&nbsp;of&nbsp;the&nbsp;output:&nbsp;'&nbsp;</span><span style="color: #007700">.&nbsp;</span><span style="color: #0000BB">$last_line&nbsp;</span><span style="color: #007700">.&nbsp;</span><span style="color: #DD0000">'<br />&lt;hr&nbsp;/&gt;Return&nbsp;value:&nbsp;'&nbsp;</span><span style="color: #007700">.&nbsp;</span><span style="color: #0000BB">$retval</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
    </div>

   </div>
  </p>
 </div>


 <div class="refsect1 notes" id="refsect1-function.system-notes">
  <h3 class="title">注释</h3>
  <div class="warning"><strong class="warning">Warning</strong><p class="para">当用户提供的数据传入此函数，使用
<span class="function"><a href="function.escapeshellarg.html" class="function">escapeshellarg()</a></span> 或 <span class="function"><a href="function.escapeshellcmd.html" class="function">escapeshellcmd()</a></span>
来确保用户欺骗系统从而执行任意命令。</p></div>
  <blockquote class="note"><p><strong class="note">Note</strong>: <p class="para">如何程序使用此函数启动，为了能保持在后台运行，此程序必须将输出重定向到文件或其它输出流。否则会导致
PHP 挂起，直至程序执行结束。</p></p></blockquote>
  <blockquote class="note"><p><strong class="note">Note</strong>: <span class="simpara"><a href="features.safe-mode.html" class="link">安全模式</a> 启用时，可仅可用
<a href="ini.sect.safe-mode.html#ini.safe-mode-exec-dir" class="link">safe_mode_exec_dir</a> 执行文件。实际上，现在不允许在到可执行的路径中存在 <em>..</em> 组件。</span></p></blockquote>
  <div class="warning"><strong class="warning">Warning</strong><p class="simpara"><a href="features.safe-mode.html" class="link">安全模式</a> 启用时，命令字符串会被
<span class="function"><a href="function.escapeshellcmd.html" class="function">escapeshellcmd()</a></span> 转换。因此，<em>echo y | echo x</em> 会变成
<em>echo y \| echo x</em>。</p></div>
 </div>


 <div class="refsect1 seealso" id="refsect1-function.system-seealso">
  <h3 class="title">参见</h3>
  <p class="para">
   <ul class="simplelist">
    <li class="member"><span class="function"><a href="function.exec.html" class="function" rel="rdfs-seeAlso">exec()</a> - Execute an external program</span></li>
    <li class="member"><span class="function"><a href="function.passthru.html" class="function" rel="rdfs-seeAlso">passthru()</a> - Execute an external program and display raw output</span></li>
    <li class="member"><span class="function"><a href="function.popen.html" class="function" rel="rdfs-seeAlso">popen()</a> - 打开进程文件指针</span></li>
    <li class="member"><span class="function"><a href="function.escapeshellcmd.html" class="function" rel="rdfs-seeAlso">escapeshellcmd()</a> - Escape shell metacharacters</span></li>
    <li class="member"><span class="function"><a href="function.pcntl-exec.html" class="function" rel="rdfs-seeAlso">pcntl_exec()</a> - 在当前进程空间执行指定程序</span></li>
    <li class="member"><a href="language.operators.execution.html" class="link">backtick operator</a></li>
   </ul>
  </p>
 </div>

</div><hr /><div class="manualnavbar" style="text-align: center;">
 <div class="prev" style="text-align: left; float: left;"><a href="function.shell-exec.html">shell_exec</a></div>
 <div class="next" style="text-align: right; float: right;"><a href="book.pthreads.html">pthreads</a></div>
 <div class="up"><a href="ref.exec.html">Program execution 函数</a></div>
 <div class="home"><a href="index.html">PHP Manual</a></div>
</div></body></html>
